Presented herein is a novel method for the efficient, ambient temperature generation of sulfonyl radicals from aryl and alkyl sulfonylbromides upon autoxidation of triethylborane (Et3B). The resultant radicals were regioselectively trapped via addition to terminal alkynes, generating a secondary vinyl radical that selectively abstracts a Br atom from RSO2Br, yielding the (E)-bromo vinylsulfones. Sensitivity towards Lewis basic groups was observed, presumably due to the disruptive coordination to Et3B before atom-transfer.

[26]
The singly occupied orbital can serve as both the electron donor and acceptor. According to NBO analysis, the donor character dominates as follows from the relative energies of n→σ*C-S (17.8 and 9.0 kcal mol–1 for α and β spins, respectively) and σC-S →n (<0.5 and 6.6) interactions (for the adduct of tosyl radical and 1-hexyne). The vinyl radical of the phenylacetylene additions displayed an unusual Lewis structure (hypervalent carbon) which precluded the analysis of hyperconjugative interactions.